The present invention relates generally to light strips and, more particularly, to an integral single piece light strip containing light emitting diodes, and a process for forming such a light strip, in which the diodes and associated circuitry are protected from moisture ingress and from other potential causes of damage.
Light emitting diode (LED) light strips are commonly used to provide visual pathways or marked locations in otherwise dark, unlit areas. Such LED light strips are advantageous when compared to bulb or lamp-based markers in that the strips are relatively inexpensive to manufacture and are relatively easy to install. Further, the LEDs used in these light strips typically have a longer life than conventional lamps or bulbs.
Present LED light strips consist of circuitry including a plurality of LEDs mounted on a substrate and connected to electrical conductors. The circuitry is encased within a tube-like, partially transparent protective sheathing and connected to a power source for selective LED illumination. Two exemplary types of LED strips are described generally in U.S. Pat. No. 5,130,909 to Gross, issued Jul. 14, 1992 and entitled "Emergency Lighting Strip" and U.S. Pat. No. 4,597,033 to Meggs et al., issued Jun. 24, 1986 and entitled "Flexible Elongated Lighting System." Such strips are utilized in a variety of indoor and outdoor configurations such as emergency pathway markers, exit door indicators and ornamental lighting arrangements.
Regardless of the application, it is imperative that the LED circuitry is housed within some type of protective sheathing. The protective sheathing must be of sufficient strength to prevent damage to the circuitry due to excessive loads, such as the weight of machinery, being directly applied to the strip. Further, because the LED circuitry is highly susceptible to damage and malfunction caused by exposure to moisture, the protective sheathing must be impervious to moisture.
While the aforementioned LED light strips protect the circuitry housed within, the strips have associated limitations. The tube-like sheathings typically used as housings for present LED light strips provide minimal protection against mechanical damage to the LED circuitry due to excessive loads placed on the sheathings. Further, the aforementioned light strips provide the LED circuitry with only limited protection from moisture. The sheathing seals or strip ends through which the LED circuitry is inserted are typically susceptible to moisture penetration. Further, protective sheathings such as those described in the above-mentioned patents are substantially hollow, thereby increasing the susceptibility of such sheathings to moisture condensation. As a result, such light strips often prove to be unreliable from a moisture protection standpoint, especially in outdoor lighting applications or other applications in which the strips are exposed to extreme weather conditions. Consequently, it would be desirable to encase the LED circuitry in a more permanent type of protective sheathing that did not have the above mentioned drawbacks associated with tube-like sheathings.
One such type of permanent protective sheathing is commonly used for encapsulating electroluminescent (EL) lamps and is formed by sealing a multi-layer EL lamp configuration by a conventional sheet, or hard, lamination process. In this conventional hard lamination process, a top layer of protective film is either adhesively bonded or thermally fused to a bottom layer of protective film through the use of high temperatures and high pressure rollers, thereby sandwiching the EL lamps between the layers.
While EL strips formed through the above hard lamination process provide a layer of protection, the multi-layer EL lamps housed within such strips are also susceptible to moisture damage. Moisture is often capable of penetrating into the interior of the two-piece strips through the fused or bonded seal joining the two-piece housing, especially when the strips are utilized in outdoor applications or after the bonded or fused seal connecting the two-piece housing weakens upon aging of the strip. In addition, such a hard lamination process would not be desirable for use with LED circuitry. EL lamps include multiple layers of substantially flat conductive and non-conductive material that are easily sandwiched between top and bottom laminate layers. Conversely, because LEDs in LED light strips typically have a height of 0.040 inch or more, the high pressure rollers typically used to bond or fuse the two-piece housing could crush protruding LEDs during formation of an LED strip. In addition, the high temperatures associated with the bonding or fusing steps in a hard lamination process would subject the LEDs and associated circuitry to heat damage, thus rendering an LED strip manufactured by such a process nonfunctional.
Therefore, a need exists for an improved single piece integral LED light strip that is impervious to moisture and that provides a high degree of protection against other forms of potential damaging elements. There also exists a need for a soft lamination process for producing such an elongated single piece integral LED light strip in which a protective housing encapsulates the LED circuitry so that an integral single piece LED light strip is produced in a cost effective manner without subjecting the circuitry to damaging high pressures or high temperatures.